Data from: Evidence that fertility trades off with early offspring fitness as males age

Models of aging predict that sperm function and fertility should decline with age as sperm are exposed to free radical damage and mutation accumulation. However, theory also suggests that mating with older males should be beneficial for females because survival to old age is a demonstration of a male’s high genetic and/or phenotypic quality. Consequently, declines in sperm fitness may be offset by indirect fitness benefits exhibited in offspring. While numerous studies have investigated age-based declines in male fertility, none has taken the integrated approach of studying age-based effects on both male fertility and offspring fitness. Here, using a cohort-based longitudinal study of zebrafish (Danio rerio), we report a decline in male mating success and fertility with male age but also compensating indirect benefits. Using in vitro fertilisation, we show that offspring from older males exhibit superior early survival compared to those from their youngest counterparts. These findings suggest that the high offspring fitness observed for the subset of males that survive to an old age (~51 % in this study) may represent compensating benefits for declining fertility with age, thus challenging widely held views about the fitness costs of mating with older males.

衰老模型预测，精子功能与生育力会随年龄增长而下降，因为精子会遭受自由基损伤与突变积累的影响。不过相关理论同时提出，与年长雄性交配对雌性而言是有益的，因为能够存活至老年本身就证明了雄性具备较高的遗传与/或表型质量。因此，精子适合度的下降或许可被后代所体现的间接适合度收益所抵消。尽管已有大量研究探讨了雄性生育力随年龄的下降趋势，但尚无研究采用整合性方法，同时探究年龄对雄性生育力与后代适合度的双重影响。本研究以斑马鱼（Danio rerio）为研究对象开展队列纵向研究，结果显示雄性的交配成功率与生育力随雄性年龄增长而下降，但同时存在补偿性的间接收益。通过体外受精实验，我们发现年长雄性的后代相较于最年轻雄性的后代，早期存活率更具优势。这些研究结果表明，在活到老年的雄性亚群（本研究中该亚群占比约51%）中观察到的高后代适合度，或许可以抵消生育力随年龄下降带来的损失，从而挑战了学界关于与年长雄性交配存在适合度成本的普遍认知。